Up until a couple months back I was getting a little over 300 miles to a single tank of gas. The check eng light came on, and after some investigating, went to a dealership and bought a new DPFE sensor, and swapped it out with the old one. Now, Im only getting about 250-260 miles to a tank. My driving hasn't changed, and Im still buying my gas at the same stations.

Would changing the DPFE sensor cause this, or could something else have happened that I havent noticed around the same time to cause this drop in MPG?

that sensor is part of the control for the EGR function, so it is possible that your MPG could have changed upon replacement. What might be more likely is that if you cleared codes or disconnected the battery, you've erased your adaptive trims (ex. fuel, spark, EGR, transmission, etc.) so it might take a tank or two worth of driving to fully re-adapt. So I'd give it a little time to see if it it improves (assuming it is running well).

Thanks for the reply. Its been well over a couple tanks of gas, I think I changed it early December. About the same time, the transmission started doing the ever so common 'feels like im driving over rumble strips' thing. Could this be the culprit to my lowered MPG?